html,body{
    height: 100%;
    margin: 0;
    padding: 0;
}
.main{
    width: 300px;
    height: 200px;
    background-color: #f00;
    /*border-width: 5px;*/
    border: 8px solid #00f;
    margin: 20px auto;
    padding: 5px;
}